Compaction measurement is of great significance in the construction of highways, airports, railway embankments, trench backfills, dams and foundations. The knowledge of material density can be a major indicator of how well a resident structure will perform its intended usage. Under compaction can cause serious deformation and settlement of the structure, while over compaction can cause cracks that affect the required material strength. Also, in-place density measurements are necessary to ensure proper testing of asphalt paving used in highways, airports and parking lots. Either by design choice or to comply with standards and/or job requirements, density measurements are used as a field quality control test for monitoring the compaction of soil, asphalt and concrete structures.
Nuclear gauges are the standard method of density measurement in most heavy construction projects. Various State Departments Of Transportation (DOT), as well as the Federal Highway Administration (FHWA), have adopted specifications for use of nuclear density gauges. Nuclear gauges are used to determine compliance with the specification for construction projects. While, there are numerous testing methodologies in use to measure structure density, nuclear testing devices are the preferred standard around the world, due to their speed, accuracy, and convenience.
Older, more primitive testing methods such as sand cone (soils), balloon (soils) and core samples (asphalt) testing are time-consuming and involve taking samples of the test materials off-site for analysis. Results are often not available for as long as 24 hours after sampling, which is especially problematic in asphalt construction projects. These testing processes are labor-intensive and necessarily involve the destruction of small pieces of the structure material. Nuclear gauges, on the other hand, are portable devices which are placed on the material and automatically display the material density in as little as 15 seconds.